GB1363109A - Monitoring knocking in an internal combustion engine - Google Patents

Abstract

1363109 Monitoring knocking in an I C engine SNAM PROGETTI SpA 22 Sept 1971 [22 Sept 1970] 44288/71 Heading G1N Apparatus monitoring knocking in an I. C. engine having a combustion chamber and an ignition system for periodically igniting fuel in the combustion chamber comprises a Piezoelectric accelerometer 1 coupled mechanically to the engine head and transducing engine vibrations into a train of electrical signals characteristic thereof, a gate 8 of which a signal input is connected to the accelerometer output and controlled in dependence upon the ignition system so as to block signals at the gate input except during a predetermined interval in each operating cycle of the engine, the interval commencing after a proportion of the period of the operating cycle has elapsed following ignition of the fuel in the combustion chamber the proportion being such that the pressure in the combustion chamber is at substantially its maximum value at the end of that proportion of the period and the gate being opened for an interval corresponding to 60 degrees to 80 degrees of each engine crankshaft revolution. The gate control signals are derived by an inductive probe 3 giving an output pulse for each ignition pulse which pulse is shaped at 4 to drive bi-stable multi-vibrator 5 delivering complementary pulse train signals 18, 19 to half-cycle integrators, of which one 6 employs signal 18 to charge an integrating capacitor at constant current to a peak voltage inversely proportional to the frequency of the ignition pulses. The integrator 6 provides two output signals to charge respective capacitors 16, 17 during each half-cycle of the signal 18 during which it is at level 1. In each following half cycle the capacitors are discharged at constant current, the discharge time constants of capacitors 16, 17 being chosen so that the capacitor 16 reaches a substantially fully discharged condition before the capacitor 17. The voltages across these two capacitors being applied to a logic circuit 9 applied to a control input of the gate 8. As indicated by the dashed line output from multi-vibrator 5 and dashed line input to gate 8 the signal 19 is treated in a similar manner to the gate 18.